Internal combustion engine



Nov. 23, 1943. A; G.'F. WALLGREN Ipmamuu. cdMBusTIoN ENGINE Filed Dec. 25, 194i 2 sheets sheet 2 A ATTORNEY INVENTOR Patented Nov. 23, 1943 INTERNAL COMBUSTION ENGINE August Gunnar Ferdinand Wallgren, Eskilstuna, Sweden Application December 23, 1941, Serial No. 424,110 In'Sweden January 15, 1941 9 Claims;

The invention relates to internal combustion engines in which the cylinder is formedwith ports adapted tobe uncovered at'the end of the working stroke of the engine piston. Air under a pressure above atmospheric is introduced into the cylinder through said ports for the purpose of scavenging the cylinder of remaining combustion gases. The scavenging air is compressed in the crank casing or with the aid of a special compressor. More particularly, the invention relates to such engines in which the combastion gases escape through exhaust ports in the cylinder walls, said ports being located adjacent to the inlet ports for the fresh air, and being uncovered by the piston somewhat before the latter ports. The scavengingof the cylinders is more or less incomplete, a portion of the fresh air flows directly to the exhaust ports instead of entering the more remote parts of the cylinder space so as to expel the exhaust gases remaining therein.

For this reason it is known to form the piston as a guide blade member so that the air entering through the inlet ports will be caused to flow toward the central portion of the cylinder, before the air flows out through the exhaust ports. This known construction, however, has the drawback among other things, that stresses and strains are set up in various parts of the piston on account of the great temperature differences between them. It is the main object of the invention to provide guide blades which are adapted to expand and to contract freely relatively to the pistons under the influence of the temperature in the cylinders and'which ensure a highly improved scavenging of the cylinder. Another objectof the invention is to increase the output obtained from the engine.

Further objects and advantages of the invention will be apparent from the following description considered in connection with the accompanying drawings which form a part of this specification, and of which: v

Fig. l is a longitudinal section through a portion of a two stroke cycle engine constructed in accordance with the invention, the piston of the engine being illustrated in its extreme position upon a completed working stroke;

Fig.2 isa similar section to that in Fig. 1, but withthe piston taking its opposite extreme position;

Fig. 3 is anendwise view of the piston andof guide blade members arranged on the same;

Fig. 4 show s the cylinder cover of the engine viewed from below.

In the drawings, l 0 designates the engine cylinder; l2 the piston working in said cylinder, and M a cylinderhead. The cylinder wall is formed with two groups of ports l6 and I8. The ports of each group are preferably distributed about the whole circumference of the cylinder. During the working stroke of the piston the same will first uncover the exhaust ports I'6, which are in communication with an exhaust passage 2|], and then the intake ports I8, which in the present form of embodiment communicate with the crank case (not shown) of the engine through passages 22. The ports 18 may preferably be inclined so that the air is circulated when entering the cylinder space. The formed in a similar manner.

Guide blades 24 are provided round the circumference of the upper surface of the piston. Each of these guide blades extend over only a portion of the circumference, and their radially extending edges are spaced apart with a small play so as to form together a guide blade ring about the edge of the cylinder. Each one of the guide blade members 24 is preferably connected at the center thereof to the piston by means of a screw 26. The guide'blade members are preferably constructed from. sheet-metal of fire-report s l6 may be sistive steel, while the piston may consist of a lower-grade material in this respect which is consequently cheaper. The distance between the piston and the guide blades adjacent to the ports I8 may be approximately equal to the height of the ports. The radially extending inner edges of the guide blade members are preferably extended down toward the piston (see Figs. 1 and 2); The piston head is formed with a recess 23, and the guide blades inclining inwardly toward the center of the piston extend for a distance over said recess, for instance about half of the piston radius. The central portion of the recess 28 preferably may have slightly conical walls.

The cylinder head I4 has an annular recess 30 corresponding to the shape of the guide blades. In order to keep the compression space within suitable dimensions, when the piston is in the position shown in Fig. 2, the central portion of the cylinder head is extended downwardly so as to form bosses 32 protruding into the combustion space. Between these bosses the fuel is injected through a nozzle 34. In order that the fuel shall then be spread in the cylinder space, thereare provided passages 36 between the bosses, said passages extending radially outwardly from the nozzle 34.

When the piston is at the lower end of its working stroke, it will first open the exhaust ports 16, the combustion gases then commencing to escape from the cylinder space through these ports and through the passage 20. During the continued movement of the piston, the ports l8 are also opened, and air compressed in the crank case then flows in through the ports l8 so as to be carried inwardly by the guide blades 24 toward the central portions of the cylinder space. The air, to which a rotary motion may be imparted by the inclination of the ports I8, is preferably first directed somewhat inwardly toward the piston, and then flows centrally upwards in the cylinder space while performing a kind of cyclonic movement, and then to turnsin the upper part of the space so as to flow downwardly at the peripheral portion thereof to the exhaust ports i6. During this flow an efiective scavenging of the remaining combustion gases is ensured. It is important that the distance between the two groups of ports I6 and it be such relatively formed in the wall thereof, a piston reciprocable within said cylinder to thereby uncover said port, a plurality of spaced segment-shaped guide members separate from the piston for directing the flow of scavenging air admitted to said cylinder when said port is uncovered, and means for to the height of the guide blade passages at the'cylinder wall, that the air in the crank case cannot now directly to the discharge ports it, or can do so to a very slight extent only, when the piston moves upwardly from the loiver dead position. This distance consequently should be so great that the piston closes the passages 22 when the guide blade passages'commence to pass over the ports [6 during the compression stroke. In order that the ports IGand l8 shall not have too great an extent in the direction of the cylinder axis, it is-suitableto make the ports Hiv and iii of less vertical extent but wider than normally, so that the desired passage area through the same is maintained.

As will be found from the above, the guide blade apparatus is composed of members which may freely expand and contract relatively to the piston, so that dangerous stresses and strains will not be produced in or between the same.

The piston I2 is preferably formed in such manner as to also permit of being used without any changes idconstructions where there isno guide blade apparatus.

While more or less specific embodiments of the inventionhave been shown, it is to be understood that the same are for purpose of illustration only, and thatthe invention is not to be limited thereby, but its scope'is to be determined by the appended claims.

What I claim is:

1. In :an internal combustion engine, a cylinder having, an inlet port for scavenging air formed in the wall thereof, a piston reciprocable within said cylinder to thereby uncover said port,

guide means carried by said piston and separate from the working face thereof for directing the flow of scavening air admitted to said cylinder when said port is uncovered, and means for securing said guide means to said piston to have movement relative to said face due to expansion and contraction.

2. In an internal combustion engine, a cylinder having an inlet port for scavenging air formed in the wall thereof, a piston reciprocable within said cylinder to thereby uncover said port, a plurality of guide members separate from each other and from the piston for directing the flow of scavenging air admitted to said cylinder when said port is uncovered, and means for securing each guide member to said piston so as to permit the guide members to expand and contract independently of each other and of the piston.

3. In an internal combustion engine, a cylinder having an inlet port for scavenging air individually securing each guide member to said piston so as to permit the guide members to expand and contract independently of each other and of the piston.

4. In an internal comb'ustlon engine, a cylinton head and the guide means for directing the flow of scavenging air towards the center of said cylinder when said port is uncovered.

5. Inan internal combustion engine, a cylinder having an inlet port for scavenging air formed in the wall, thereof, a piston having a concave head reciprocable within said cylinder to thereby uncover said port, guide means separate from and carried by said head, said guide means being in the form of a hollow frustrated cone with the end of smaller diameter towards said concave head, and means for securing said guide means to and in spaced relation from said head so as to permit the guide means to expand and contract independently of the piston and to provide an inwardly and downwardly extending passage between the concave piston head and the guide means for directing the flow of scavenging air when said port is uncovered.

, 6. In an internal combustion engine, a cylinder having a plurality of elongated inlet ports for scavenging air distributed around the cylinder, a piston reciprocable within said cylinder to thereby uncower said ports, guide means separate from and carried, by the head of said piston, said guide means being in the form of a hollow frustrated cone with the end of smaller diameter extending towards the piston head, and means for securing said guide means to and in spaced relation from the piston head so as to permitthe guide means to expand and contract independently of the piston and to provide a passage between the piston head and the guide means for directing the flow of scavenging air towards the center of said cylinder when said ports are uncovered, said ports being inclined with respect to the axis of the cylinder.

7. In an internal combustion engine, a cylinder having an inlet port for scavenging air formed in the wall thereof, a cylinder head, a piston reciprocable within said cylinder to thereby uncover said port, guide means separate from and carried by the head of said piston, said guide means being in the form of a hollow frustrated cone with the end of smaller diameter extending towards the piston head, means for securing said guide means to and 'in spaced relation from the piston head so as to permit the guide means to expand and contract independently of the piston and to provide a passage between the piston head and the guide means for directing the flow of scavenging air towards the center of said cylinder when said port is uncovered, said cylinder head having a projecting portion shaped to conform generally to the conical recess formed by said guide means, said projecting portion having a centrally located recess and a fuel injection nozzle located in the last-mentioned recess, said projecting portion being formed with grooves extending radially from said last-mentioned recess.

8. In an internal combustion engine, a cylinder havingan inlet port for scavenging air formed in the wall thereof, a piston reciproc'able within said cylinder to thereby uncover said port, guide means separate from and carried by said piston for directing the flow of scavenging air admitted to said cylinder when said port is uncovered, said guide means being made of a material which is more heat resistant than said piston, and means for securing said guide means to said piston" so as to permitthe guide means to expand and contract independently of the piston.

9. In an internal combustion engine, a cylinder having a plurality of inlet ports for scavenging air distributed around the cylinder and a plurality of exhaust ports distributed around the cylinder above said inlet ports, a piston reciprocable within said cylinder to thereby uncover first said exhaust ports and then said inlet ports, guide means separate from and carried by said head of said piston, and means for securing said guide means to and in spaced relation from the piston head so as to permit the guide eans to expand and contract independently of the piston, said guide means having a centrally located aperture whereby to form with said piston head a passage for-directing air,

admitted through said inlet ports, towards the center of the cylinder and for preventing direct passage of said air to said exhaust ports.

AUGUST GUNNAR FERDINAND WALLGREN. 

